2 (Dicyanomethylene)croconate

2-(Dicyanomethylene)croconate is a divalent anion with chemical formula C
8N
2O2−
4 or ((N≡C−)₂C=)(C₅O₄)²⁻. It is one of the pseudo-oxocarbon anions, as it can be described as a derivative of the croconate oxocarbon anion C
5O2−
5 through the replacement of one oxygen atom by a dicyanomethylene group =C(−C≡N)₂.

The anion was synthesized and characterized by A. Fatiadi in 1980, by hydrolysis of croconate violet treated with potassium hydroxide. It gives an orange solution in water.